Sealant for a concrete element and method for producing a sealant

ABSTRACT

A sealant for a concrete element, having a planar carrier and an active substance applied onto the carrier, wherein the active substance is designed to be chemically reactive with water. The carrier is flexible.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC 119 of European PatentApplication No. 17156627.6, filed Feb. 17, 2017, the disclosure of whichis herein incorporated by reference.

BACKGROUND OF THE INVENTION

The invention relates to a sealant for a concrete element, comprising aplanar carrier and an active substance applied onto the carrier, whereinthe active substance is designed to be chemically reactive with water.

Buildings are being designed more and more nowadays as water-impermeableconcrete structures.

To this end, it is known in the related art to seal joints, cracks, andthe like in a concrete element by means of subsequent crack injections.Each crack must be treated individually in this case, however. Inaddition, regular inspections are required in order to search for andtreat any new cracks that may have developed.

Alternatively, so-called fresh concrete composite films are utilized forthe planar sealing of a concrete element. These fresh concrete compositefilms are applied onto the concrete element to be sealed. They achievetheir sealing effect by way of an integrated film which is made, forexample, of PVC or PE.

It is disadvantageous in this case that moisture can no longer reach theconcrete element once such a fresh concrete composite film has beenapplied. In particular, a rehydration, which is desirable in principle,is therefore prevented. If the fresh concrete composite film becomesdamaged over the course of time, or if it begins to tear due to aging,the protective effect of the film is lost over a large area.

EP 0 992 466 B1 describes a sealing element which comprises awater-repellent admixture instead of an active substance applied ontothe carrier. The water-repellent admixture can be physically dissolvedin alkaline media, so that a (water-swellable) active substance canbegin to swell.

EP 1 571 271 B2 describes a sealing device for sealing work joints, inwhich the carrier is designed as a galvanized carrier sheet and istherefore rigid. In order to seal the work joint, the sealing device isintroduced into the work joint.

It is also known to embed bentonite, which swells highly upon contactwith water, between two geotextiles. Such a sealant is utilized, forexample, in landfill construction and acts by allowing moisture topenetrate up to the bentonite over time, so that the bentonite swellsand ultimately develops the sealing effect.

SUMMARY OF THE INVENTION

The problem addressed by the invention is that of improving a sealantfor a concrete element of the type in question.

The problem is solved by a sealant for a concrete element, comprising aplanar carrier and an active substance applied onto the carrier, whereinthe active substance is designed to be chemically reactive with water,and wherein the carrier is flexible.

The active substance can be applied on the carrier so as to bedissolvable from the carrier. In particular, the active substance can bedissolvable from the carrier in an alkaline medium and/or by means of amedium, in particular an alkaline, hydrous medium. In this case, it canbe provided that the active substance comprises substances which can bedissolved out of the active substance and have, in particular, amechanical and/or chemical sealing effect. For example, the activesubstance can include a limestone-forming substance.

The flexible carrier can be, in particular, not rigid, i.e., inherentlymovable. The carrier can be inelastically flexible. Since the carrier isflexible, the sealant can be even more easily handled, in particular thesealant can also be situated on concrete elements having an unevensurface. The sealant can therefore be utilized both for sealing joints,in particular work joints, and for sealing, in particular, unevensurfaces of concrete elements. The concrete elements and/or concretesurfaces of the concrete elements can be situated so as to have contactwith the earth. They can also be exposed to water.

Since the active substance has been applied onto the flexible carrier,incoming moisture can very easily reach the active substance. The activesubstance can then chemically react with the moisture. The moisture orwater can come, for example, from a concrete edge zone of a freshlyprepared concrete element, on which the sealant is situated. Themoisture can also come from the surroundings.

The water can be alkaline and/or the active substance can be designed tobe chemically reactive with alkaline water.

Properties, in particular sealing properties, of the sealant cantherefore also be automatically modified by means of chemical reactionsafter production or after processing. Such a modification can alsoextend over a relatively long period of time, and therefore such amodification can also take place continuously. The modifications canalso be limited to one or multiple areas of the carrier, in particulardepending on the planar distribution of the moisture.

The quantity of incoming moisture can also depend on whether cracks,defective spots, or the like are locally present in the sealant and/oron a concrete element onto which the sealant has been applied.

It can be provided that the sealant is at least slightly water-permeableafter the production thereof, in particular before the use thereof forsealing a concrete element.

The water-permeability can be measured on the basis of the permeabilitycoefficient. In particular, the sealant can be at least slightlywater-permeable when it has a permeability coefficient of at least 10⁻⁹m/s.

A particularly favorable sealing effect can be achieved when thepermeability coefficient is between 10⁻⁹ m/s and 10⁻⁸ m/s.

The permeability coefficient can also be up to 10⁻⁴ m/s. In this case,active substance can particularly easily reach the concrete element. Inparticular, the active substance can be actively dissolved out by meansof the alkalinity of the concrete element, in particular in the case offresh concrete. The active substance can then chemically react in and/oron the concrete element.

Therefore, moisture can reach the concrete element through the sealanteven after the sealant has been applied onto the concrete element. Theconcrete element can absorb moisture and, for example, rehydrate. Theconcrete element, in particular a concrete edge zone of the concreteelement, can therefore also reseal.

By way of an initial flow of water or moisture through the sealant,which is deliberate yet is limited by the sealant, active substance canbe conveyed from the carrier to the concrete element and, at theconcrete element, can support and/or actively initiate a local sealing.The active substance can also play a catalytic role, in particular forthe self-sealing of the concrete element.

In this way, in particular, cracks, defective spots, or the like can besealed locally in the area of a crack or a defective spot or the like.In other words, the sealant can deploy its effect, in particular, wherethe sealing effect is “required”, since stronger moisture flows alsogenerally occur in these areas. Any cracks in the concrete element cantherefore be sealed in the sense of a “self-healing” of the concreteelement (and not only of the sealant itself).

In contrast to the fresh concrete composite film described at theoutset, the sealant according to the invention can therefore not onlyact as a moisture barrier or obstacle by itself, but can also activelycontribute to an improvement in the tightness of the concrete elementitself. Even when the sealant has been locally damaged and, therefore,the water permeability in the area of the damage is increased, thesealing effect can be at least largely retained for the remaining sealedareas and possibly even for the damaged area.

It can also be provided that the sealant changes its water-permeabilityover the course of time, proceeding from the water-permeability of thesealant which existed after the sealant was produced. In this way, thesealant can be designed, for example, to be self-swelling and,therefore, can reduce its water-permeability over the course of time. Ifsuch a sealant is damaged, the damaged area can therefore also beautomatically partially or completely eliminated by way of the sealant.

It can be provided that the carrier is designed as a geomembrane, ageotextile, a film and/or a nonwoven fabric, in particular as a PPnonwoven fabric, a PE nonwoven fabric, a PE woven fabric, a PP wovenfabric, a nonwoven fabric-woven fabric combination, particularlypreferably as a mechanically joined nonwoven fabric-woven fabriccombination.

Such geomembranes, geotextiles, and/or nonwoven fabrics are available atlow cost and can cover and seal even large concrete elements. Such acarrier can also contribute to the reinforcement, to the post-treatmentof the concrete edge zone, and/or to the reduction of pores in theconcrete element.

It is also conceivable that the active substance comprises or is acement, quartz, a silicate, an ash, in particular fly ash, a calciumhydroxide, a carbonate, in particular a hydrogen carbonate, anon-hydrogen carbonate, and/or a calcium carbonate.

Such an active substance can make sealing possible in a chemical,physical and/or mechanical way. In particular, it is possible that asealing effect can be achieved both by means of the sealant as well asby a concrete element to be sealed.

The active substance can be swelling in order to achieve a physicalseal. For example, cement or cement stone contained in the activesubstance can swell. As a result, the initial water-permeability of thesealant can be reduced, in particular after a defined period of time haselapsed or over a defined period of time. Cement or cement stonecontained in the active substance applied on the carrier can also betransported to the concrete element and, at that point, can swell and,for example, locally close cracks or pores in the concrete element.

A chemical sealing effect can be achieved, in particular, by rehydratingcement or cement stone and/or by forming (water-insoluble) calciumcarbonate.

A mechanical seal can be achieved by constricting or blocking a flowpath by means of anorganic or organic fines, for example quartz silicateor ash. It is understood that other active substances, such as cement,calcium hydroxide, or carbonate, as fines can also deploy a mechanicalsealing effect, in particular in a supplementary manner.

A particularly favorable sealing effect can be achieved by means ofcrystallization or sintering. For this purpose, calcium carbonate, inparticular, can be provided in the active substance or can be releasedby the active substance. The calcium carbonate can deposit on theconcrete element, along the flow path of the water, and, there, plug andseal cracks or the like.

Such a mechanical crack closure can be achieved, in particular, in aninitial phase by means of such fines or particles.

It is conceivable, in particular, that the active substance contains anadhesion promoter.

The adhesion promoter can be water-insoluble. The adhesion promoter canbe soluble in an alkaline medium. It is also conceivable that theadhesion promoter is water-permeable.

The adhesion promoter can be mixed, as a dispersion, into the activesubstance. In particular, the active substance can include a dispersingphase having an adhesion-promoting effect.

As a result, the active substance can be applied onto the carrier andcan adhere thereto in an improved way, thereby making it easier to applythe active substance and subsequently use the sealant, for example at aconstruction site.

In particular, the active substance can include the adhesion promoter,in particular as a dispersion and/or a dispersing phase, as the firstcomponent, and, as a second component, a cement, a calcium hydroxide,and/or a mixture of quartz, a silicate, fly ash, a non-hydrogencarbonate, and a hydrogen carbonate.

In other words, the substance can also contain the adhesion promoter,for example as a plastic dispersion. To this end, the adhesion promotercan be incorporated into the remaining active substance or can be mixedtherewith. The subsequent sealing material or the second component canthen be easily applied on the carrier and, therefore, at leasttemporarily fixed. In other words, the active substance can be capableof adhering particularly well. In particular, it can also form asheet-like unit.

The active substance can include an elasticizer. The elasticizer can be,for example, a plastic-based substance. For example, the elasticizer canbe a plastic dispersion and/or a dispersing phase of a plasticdispersion. The elasticizer can be designed, in particular, for reducingthe brittleness of at least one other component of the active substance,for example cement, and/or for improving the elasticity thereof. Theelasticizer can also be designed for improving the elasticity and/orflexibility of the active substance applied on the carrier.

In general, the active substance can include a type of a dispersingphase. The active substance can also include at least two differenttypes of a dispersing phase. For example, a first type of a dispersingphase can have an adhesion-promoting property and/or can be an adhesionpromoter, and a second type of a dispersing phase can have anelasticizing property and/or can be an elasticizer.

In other words, a dispersion, preferably at least two different types ofdispersions, can be incorporated into the active substance duringproduction.

The dispersion can be, for example, a latex dispersion or awater-plastic dispersion.

The active substance can include, preferably as a dispersion or in theform of a dispersing phase, vinyl acetate-ethylene, an ethylene-vinylacetate copolymer and/or vinyl acetate.

The active substance can also include a preferably water-swellablepolymer, in particular a liquid dispersion polymer or a superabsorbentpolymer. The mass fraction of the polymer with respect to the activesubstance can be between 40% and 60%, in particular 50%.

The polymer, in particular the liquid dispersion polymer or thesuperabsorbent polymer, can have a high swelling volume and/or can beadhesion-promoting. The polymer can be incorporated into the activesubstance in order to produce the active substance as a dispersion. Inparticular, the polymer can be contained in the active substance as adispersing phase.

When water flows through, the polymer can therefore swell to aparticularly strong extent and reduce the water-permeability of thecarrier. As a result, the water flow through the carrier can be reduced,in particular after the active substance or a component of the activesubstance has washed onto the concrete element. A depositing, sintering,and/or reaction of the active substance or the component on or with theconcrete element and, therefore, the local sealing effect, can thereforebe further improved.

The polymer itself can also be provided as a carrier. In this case, itcan be advantageous, in particular, that the polymer, in particular theliquid dispersion polymer and/or the superabsorbent polymer, can havegood adhesion on concrete. Therefore, the polymer or the carrier caneven adhere on the concrete element by itself. An additional fasteningof the sealant on the concrete element can therefore be dispensed with.Alternatively, the carrier can also be precoated with the polymer, forexample the carrier can therefore be a swelling nonwoven fabric.

The carrier (which is designed to be planar) can comprise an activesubstance on one or both of its flat sides.

For example, the carrier can comprise active substance on only one ofits two flat sides. In this case, on the other flat side which can beoriented facing away from the concrete element, for example, the sealantor the carrier can be provided with additional properties, in particularsurface properties, according to the requirements of a particularinstallation situation. If the carrier has active substance on both flatsides, however, the amount of active substance per unit of area of thecarrier can be increased.

It is particularly advantageous when the sealant has a predefinedminimum roughness on at least one flat side of the carrier.

Due to the minimum roughness, the bond between the sealant and theconcrete element can be improved. In particular, any force-fit and/orform-fit connections which may be present can also be improved by“interlocking” with the concrete element provided with the sealant.

Additionally or alternatively, it can also be provided that the activesubstance itself bonds with the concrete element. The carrier can alsoestablish a bond with the concrete element, in particular independentlyof the active substance.

It can also be provided that the sealant includes a preferably water-and/or gas-impermeable covering on at least one flat side of thecarrier. In particular, it can be provided that the covering isremovably applied on the sealant. In this case, the covering can protectthe sealant, in particular during storage until ready for use. For use,the covering can be removed from the sealant, so that the sealingeffects of the sealant can be utilized.

The covering can also generate further properties of the sealant, inparticular of a flat side of the carrier, in particular depending on theapplication. For example, the use of a covering which keepsconcrete-destroying substances away from the concrete element canfurther protect the concrete element from concrete aging.

The covering can also have, for example, a predefined minimumgas-impermeability, in particular with respect to radon and/or methane.In other words, the covering can be gas-impermeable, in particular withrespect to radon and/or methane.

The production of a sealant according to the invention, comprising aplanar, flexible carrier and an active substance, can include the stepsof:

a) equipping the carrier with an adhesion promoter, in particular as adispersion, and/or with a polymer, in particular a liquid dispersionpolymer and/or a superabsorbent polymer, and

b) applying the remaining active substance onto the carrier, inparticular by rolling or spraying the active substance onto the carrierand/or by immersing and/or impregnating the carrier into or with theremaining active substance.

Therefore, for the purpose of production, the polymer and/or thedispersion can be applied onto the carrier first, so that thesubsequently applied, remaining active substance is better fixed on thecarrier.

To this end, the active substance can be advantageously liquid at first.After the application, the active substance, in particular the adhesionpromoter contained therein, can dry on the carrier.

Alternatively, the active substance can also be initially mixed and thensubsequently applied onto the carrier, in particular being rolled on orsprayed on, and/or can be applied onto the carrier via immersion and/orimpregnation of the carrier into and/or with the active substance.

To this end, the active substance can also advantageously contain anadhesion promoter. In order to avoid premature curing, the activesubstance can be kept in motion by means of a mixer. Subsequently, yetanother, in particular water- and/or gas-impermeable covering can beapplied, preferably removably, onto the sealant, preferably on bothsides of the sealant.

The sealant can then be utilized. To this end, the covering can first beremoved on one side. The sealant can be applied, via this side, onto aconcrete element to be sealed or can be situated on the concrete elementto be sealed. The covering can be subsequently removed from the otherside. The sealant then protects and seals the concrete element.

The scope of the invention also covers a method for producing a sealedconcrete element. According to the invention, to this end,

a) one side of a formwork is equipped with a sealant according to theinvention, and

b) concrete is poured against the side of the formwork equipped with thesealant.

The formwork can be removed after the concrete element has cured. Thesealant can preferably remain on and/or in the concrete element and/orits surface.

A concrete element which has been produced using formwork technology andsealed with a sealant according to the invention can therefore befabricated in a particularly easy way.

To this end, it can be provided that the sealant is stapled onto theside of the formwork, in particular being stapled with the aid of atacker. Tacker clamps can be utilized as the fasteners.

In this case, it is possible to make use of the fact that the sealantcan be sufficiently securely fastened on the side of the formwork, onthe one hand and, on the other hand, that the stapling is sufficientlyloose or can be sufficiently easily removed, so that, when the formworkis removed, the sealant remains on the concrete element and not on theformwork.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the present invention will become apparentfrom the following detailed description considered in connection withthe accompanying drawings. It is to be understood, however, that thedrawings are designed as an illustration only and not as a definition ofthe limits of the invention.

In the drawings, wherein similar reference characters denote similarelements throughout the several views:

FIG. 1 shows a sealant according to the invention;

FIG. 2 shows the sealant with a substance applied to both sides of thecarrier;

FIG. 3 shows the sealant according the invention with a covering; and

FIG. 4 shows a formwork having the sealant and concrete attachedthereto.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Further features and advantages of the invention result from thefollowing detailed description of the invention, with reference to thedrawings. Further features and advantages of the invention also resultfrom variants of the method according to the invention, and from theclaims.

The individual features can be implemented individually, or they can becombined in any possible manner to form variants of the invention.

FIG. 1 shows a sealant 1 for a concrete element. The sealant 1 comprisesa planar carrier 2. The carrier 2 has an active substance 3, which isapplied onto the carrier. The substance 3 is designed to be chemicallyreactive with water. The carrier 2 is flexible.

Whereas in FIG. 1 the substance 3 is applied to only one side of carrier2, in FIG. 2 the substance 3 is applied to both sides of the carrier 2.

FIG. 3 shows the sealant 1 of FIG. 1. However, in this case a covering 4is also applied to the sealant 1. The covering 4 may be water- and/orgas impermeable.

FIG. 4 shows a formwork 10 and a sealant 1 being attached to the 20formwork 10. The sealant 1 comprises the substance 3, which is facingtowards a gap 11. On the other side of the gap 11 there is an existingstructure 12, which may for example be a concrete wall. Concrete may bepoured into the gap 11 such that concrete is poured against the side ofthe formwork 10 equipped with the sealant 1.

Production

Initially, a flexible carrier, for example a geotextile, can be providedas the base for the sealant. Alternatively, a flexible polymer can alsobe formed in a planar manner, in particular as a type of netting. Inthis exemplary embodiment, a netting-like or meshed, flexible geotextilecan be provided as the carrier, so that the carrier itself iswater-permeable.

Subsequent thereto, in order to produce the active substance, anadhesion promoter, in particular in the form of a plastic dispersion,and cement and a liquid dispersion polymer are initially mixed with eachother.

The active substance is then applied onto the carrier, for example beingsprayed thereon. In particular due to the liquid dispersion polymer anddue to the adhesion promoter, the active substance adheres to thecarrier, and therefore the active substance can be more easily appliedonto the carrier. The water-permeability of the sealant can be adjustedby way of the selection of the mesh width of the carrier and by way ofthe amounts of active substance applied in specific areas. In thisexemplary embodiment, the water-permeability is adjusted in such a waythat the sealant is at least slightly water-permeable.

The sealant is subsequently dried until the active substance fixedlyadheres on the carrier.

Subsequent thereto, a covering is removably applied onto the sealant, onboth sides thereof.

In one alternative variant, the sealant is completely dried and acovering is dispensed with.

Application

A concrete element to be sealed, for example a concrete element of awall, can be protected and sealed as follows:

Initially, the covering which may be present is removed on one side. Thesealant is placed onto the concrete element in a planar manner and islightly pressed thereon, if necessary. Due to the flexibility of thecarrier, the sealant conforms to the surface of the concrete element. Ifa concrete element having a large surface area is to be sealed, itsuffices to loosely overlap one portion of the sealant with a furtherportion to be situated next thereto, wherein at least one correspondingportion of the covering is first removed from the other side, ifapplicable. The portions of the sealant generally do not need to bebonded or adhered to each other, or in any other way sealed with respectto each other. A bond is established between the sealant and theconcrete element, in particular by way of a portion of the cementcontained in the active substance, and therefore the sealant ispermanently fixed on the concrete element.

Subsequent thereto, if applicable, the remainder of the covering isdetached or is removed from the sealant.

If a concrete element is to be produced and sealed using formworktechnology, then, in one variant of the method, initially at least oneside or, depending on the sealing need, multiple sides of the formworkis/are equipped with the sealant. The covering is removed in advance,for this purpose, as needed. The sealant is then stapled to the formworkusing tacker clamps. Subsequent thereto, concrete is poured against theformwork and the concrete element is thereby produced. The formwork isremoved once the concrete has cured.

According to the findings made by the inventor, it should be noted thatthe sealant adheres on the concrete and/or interlocks on and in theconcrete during the concreting and/or the curing.

If the formwork is subsequently removed, the stapled sealant detachesfrom the formwork and remains on the concrete element.

The concrete element is initially not hermetically sealed againstmoisture or water. Instead, water can penetrate up to the component, dueto the water-permeability of the sealant. Active substance can alsochemically react with the water.

Over the course of time, the sealant passes through essentially threephases, in particular.

At the beginning or in a first phase, the concrete edge zone of theconcrete element is improved by means of the carrier. Water cavities andpore structures are at least partially compensated for or are reduced.

In a second phase, active substance or one or multiple components of theactive substance is/are transported to the concrete element by themoisture or water flow passing through the sealant, in particular at thebeginning. This transport takes place, in particular, at the points atwhich there is a need for repair, i.e., in particular at cracks,defective spots, and the like. Since the flexible carrier conforms tothe concrete element, the situation is avoided in which the activesubstance or the components is/are rinsed out through a gap that mayotherwise be present between the sealant and the concrete element, andthe transport path is kept so short that a sufficient amount of theactive substance or the components reaches the concrete element.

The liquid dispersion polymer, in particular, swells during the waterflow and therefore reduces the water flow through the sealant.

In a third phase and, in particular, in conjunction with the moistureremaining on the concrete element, the transported active substance orthe components chemically react on and/or with the concrete element.Depending on the active substance or the components, a sintering takesplace, for example, whereby cracks, defective spots, and the like arepermanently plugged and, therefore, sealed.

In addition, the carrier reinforces the concrete element on the concreteedge zone and, as a result, additionally minimizes the risk of cracksforming in the future.

Whereas, in the case of a conventional fresh concrete composite film,damage, even local damage such as, for example, a small crack, generallyresults in an extensive loss of the sealing effect, the sealantaccording to the invention can still largely ensure a sealing effect orprotection of the concrete element. Since the sealing effect is notguaranteed solely by way of the tightness of the sealant itself, butrather also by way of the interplay of the sealant, the transportedactive substance and the self-healing of the concrete element at damagedareas induced thereby, the sealing effect remains largely retained.

An improved, long-lasting and, in particular, active protection of theconcrete element is therefore made possible by the sealant according tothe invention.

What is claimed is:
 1. A sealant for a concrete element, comprising a planar carrier and an active substance applied onto the carrier, wherein the active substance is designed to be chemically reactive with water, and wherein the carrier is flexible.
 2. The sealant as claimed in claim 1, wherein the sealant is at least slightly water-permeable after the production thereof.
 3. The sealant as claimed in claim 1, wherein the carrier is selected from the group consisting of a geomembrane, a geotextile, a film, a nonwoven fabric, a PE woven fabric, a PP woven fabric, and a nonwoven fabric-woven fabric combination.
 4. The sealant as claimed in claim 1, wherein the active substance comprises at last one of the following: a cement, quartz, a silicate, an ash, a calcium hydroxide, a carbonate, a non-hydrogen carbonate, and a calcium carbonate.
 5. The sealant as claimed in claim 1, wherein the active substance contains an adhesion promoter.
 6. The sealant as claimed in claim 1, wherein the active substance contains an elasticizer.
 7. The sealant as claimed in claim 1, wherein the active substance comprises at least one type of a dispersing phase.
 8. The sealant as claimed in claim 1, wherein the active substance comprises a water-swellable polymer.
 9. The sealant as claimed in claim 1, wherein the carrier comprises the active substance on one flat side or on both of flat sides.
 10. The sealant as claimed in claim 1, wherein the sealant has a predefined minimum roughness on at least one flat side of the carrier.
 11. The sealant as claimed in claim 1, wherein the sealant comprises a water- and/or gas-impermeable covering on at least one flat side of the carrier.
 12. A method for producing a sealed concrete element, comprising the following steps: a) equipping one side of a formwork with a sealant as claimed in claim 1, and b) pouring concrete against the side of the formwork equipped with the sealant.
 13. The method as claimed in claim 12, wherein the sealant is stapled onto the side of the formwork. 